Quick breaking electrical switch



Oct. 16, 1956 M. PERKINS QUICK BREAKING ELECTRICAL SWITCH 2 Shets-Sheet1 Filed July 6, 1953 bx/U 2 f 7 5 a g 1 //L,], H 2 Q g IIIH.HIIIIFILIIIIIIIIIIUMHIHHU 2 W 4 Z 0 O 5 w Q 2 a 2 Z Z Oct. 16, 1956 L.M. PERKINS I 2,

QUICK BREAKING ELECTRICAL SWITCH Filed July 6, 1953 2 Sheets-Shee 2 INVEN TOR.

United States Patent QUICK BREAKING ELECTRICAL SWITCH Laurence M.Perkins, Whitefish Bay, Wis., assignor to Allen-Bradley Company,Milwaukee, Wis., a corporation of Wisconsin Application July 6, 1953,Serial No. 366,123

7 Claims. (Cl. 200-67) This invention relates to toggle actuated snapaction switches suitable for opening and closing electrical contacts inresponse to slowly advancing actuation while maintaining substantialcontact pressure until the moment of contact throw, and it morespecifically resides in a snap action switch having a contact carryingarm displaceable between two positions of rest by the reversibletransverse force exerted by a floating toggle mechanism comprising abase anchored actuating blade and a rockable resiliently expandabletransverse force reversing member pivotally mounted on the contactcarrying arm and pivotally engaging the unanchored end of the actuatingblade.

Toggle actuated snap action switches that retain sufficient contactpressures in all stable positions of the switch are well suited forapplications where the actuating member of the toggle is advanced slowlyas in thermostatic controls and the like. In such instances a switch mayhover for considerable periods in the close vicinity of the snap overpoint and if contact damage is to be avoided contact pressure mustremain substantial during such intervals and up to the moment whenthrow-over occurs.

Toggle switches have heretofore been provided which maintain substantialcontact pressure up to the point of throwing, by providing for a storageof energy as the toggle mechanism is brought toward the snap over point.Such energy then initiates snap over before the toggle elements arealigned with the center line or the line of maximum compression of thetoggle. In switches of this type, heretofore employed, the transversecomponents determining contact pressure have been limited by the smallertoggle angles which their structures required or by resilient forcesacting within the toggle itself in such fashion as to subtract from theefiective transverse component.

It is an object of this invention to provide a snap switc in whichvanishing contact pressure at and near the throwing positions is avoidedand in which enhanced transverse force for a given toggle tension ismade available.

It is another object of this invention to provide a snap action switchin which a hammerlike blow is delivered to the contact carrier duringthe throw of the toggle after kinetic energy is built up within thetoggle and to provide in such a switch an improved degree of uniformityof response to actuating forces.

It is still another object of this invention to provide, in a switch ofthe class described, pivoted engagement between distinct toggle elementsto more accurately locate the toggle centers and to avoid subtractivetransverse forces.

These and other objects and advantages of this invention will appear inthe description to follow. In the description reference is made to theaccompanying drawings which form a part hereof and in which there isshown by way of illustration and not of limitation one specific form inwhich this invention may be embodied.

Inthe drawings:

Fig. 1 is a front view in elevation of a pressure responsive actuatorupon which a snap action switch constructed in accordance with thisinvention is mounted,

Fig. 2 is a side view in elevation of the apparatus shown in Fig. l withthe snap action switch portion thereof shown in section as viewedthrough the plane 22 in Fig. 1,

Fig. 3 is a top plan view of the apparatus shown in Figs. 1 and 2,

Fig. 4 is a side view of the contacts and contact actuating portions ofthe switch shown in Figs. 1, 2, and 3,

Fig. 5 is a side view of the contacts and contact actuating elementsshown in Fig. 4 in an alternate position of rest,

Fig. 6 is a view in perspective of the movable contact support andtoggle actuating blade which are a part of the switch shown in theprevious figures,

Fig. 7 is a view in perspective of the compression spring retainer thatforms a part of the switch, shown in the previous figures, and

Fig. 8 is a view in perspective of the compression spring and the endcup that form a portion of the switch shown in the previous figures.

The apparatus shown in Figs. 1, 2 and 3 is in form suitable for use as arefrigeration control, the same being adapted to respond to fluidpressure changes induced, for example, by temperature changes in arefrigerator. The apparatus, as shown, includes pressure responsiveparts which are related to but form no part of this invention such asinlet fitting 1 leading to and entering an expandable bellows, notshown, within a bell-shaped spring cage 2 that moves in unison with theexpansion and contraction of the bellows. Extending from the spring cage2 to the left as viewed in Fig. 2, is an actuating rod 3 that likewisemoves in unison with the bellows. The rod 3 terminates in a conicaltoggle actuator 4 that extends within a switch 5 in accordance with thisinvention and mounted as shown. The fitting 1 is mounted on the formedend of a bent metal frame 6 that forms the two sides and the back of thecontrol. A top panel 7 is turned downwardly at the front thereof forattachment to the frame 6 and to provide a support for the switch 5.

A slotted adjustment head 8 rotatably mounted on the top face of thepanel 7 engages a stamped pinion 9 directly beneath the panel 7. Thepinion 9 meshes with a compression regulating gear 10 to turn a threadedshaft 11 encircling the control rod 3 which moves a spring retainer 12,held from rotation by a pair of indicator cars 13 in slidable engagementwith oppositely disposed edges of the top panel 7. The axialdisplacement of the spring retainer 12 is measured by a scale 14 markedon the margin of the face of the panel 7 adjacent one of the indicators13. Held in compression between the spring retainer 12 and the lowerflanged edge of the bell shaped spring cage 2 is a main spring 15. Thespring 15 acts to urge the spring cage 2 rearwardly in opposition tochanging pressure within the bellows, varying in response to atemperature change. Thus, an increase in temperature causes a forwardtravel of the actuator 4 and the extent of this travel is depend entupon the loading of the spring 15 which may be adjusted by the settingof the spring retainer 12.

The switch 5 is assembled on a base 16 formed of a suitable insulatingmaterial secured by means of mounting screws 17 shown in Fig. 1. Held inplace near the top of the switch 5 by means of rivets is a pair ofstationary contact arms 18 and 19 that carry contacts 20 and 21respectively. The contacts 20 and 21 are spaced from one another infacing relationship to permit a movable contact to be positionedtherebetween.

3 The contact arms 18 and 19 are extended ,as shown to provideappropriate terminal connections 22 and 23 respectively. For adjustmentof the position of the contact a hexagonal nut 24 is seated within thebase .16' and a set screw 25 extends through the nut 24 with the tipthereof-pressing upon the back of the contact arm 18. By adjustment ofthe screw 25 the contact arm 18 and contact 20 may be sprung toward oraway from the contact 21. A third terminal'26 for connection to amovable contact is provided atthe bottom of the switch 5. Formedintegrally with the terminal 26 is a vertical finger 27 that extendsoutwardly from the base 16 to act as a stop for an actuating blade oftoggle mechanism to be hereinafter described. A second stop 49 spacedrearwardly from the finger 27 is formed by a raised portion of the base16 Anchored between the terminal 26 and the base 16 is a combinedcontact carrier and actuator 23 formed 'as a single stamping'from thinresilient sheet material positioned for movement between the stationarycon- 7 tacts 20 and 21. To increase the stiflness of the upper portionsor" the arms 38, ribs 33 are formed therein by embossing. The arms carryinwardly extending offsets to provide pivot shoulders 34 and abutments35 at the upper deflectable ends for purposes to be noted.

Member 28 includes a toggle actuating blade 36 disposed between the pairof contact arms 36 and merged integrally with the base 29. Theresilience of the material forming the member 28 is such as to permitelastic distortion or bending of the blade 36. The blade 36 isstiffened, however, along a major portion of its length by embossed ribs37, to confine a greater part of the flexure to the lower portion of theblade 36 adjacent the base 29. Upon mounting the member 28 beneath theterminal 26 electrical connection between the latter and contacts 32 isprovided.

Arms 30 and the actuating blade 36 are free to be deflected entirelyindependently of one another, and for this reason the blade 36 may beformed separately from the contact arms 34) if desired. Beryllium-copperalloy is preferred for making up the member 28, since it may be easilyformed in annealed state and then heat treated to develop the desiredresilience. The blade 36 may be formed so that under zero stress it willoccupy'a position divergent from the arms 36. The blade 36 as shown inthe drawings is so formed to render the switch in greater detail in Fig.7. The head of the retainer 38 includes a spring seat 39 formed as acentrally located boss 46 which retains a spring 46 seated thereon inits intended position. The upper margins of the spring seat 39 are cutaway to present limiting shoulders 41 and 42. Extending downwardly fromthe head of the floating toggle member, to a position in alignment withthe seat 39, is a pair of hooked fingers 43 each shaped to provide pivotnotches 44 adapted to seat upon and pivot about the pivot shoulders 34of the contact carrying arms 30. With the notches 44 bearing against theshoulders 34 and with the spring seat 39 between the abutments 35 thefloating toggle member 38 may be rocked between the positions shown inFigs. 4 and 5 which pivotal movement is limited by engagement of thelimiting shoulders 41 and 42 with the abutments 35.

Disposed between the free end 45 of the actuating blade 36 and thespring seat 39 is a compression spring 46, previously noted, one endbeing seated against the seat 39 and the opposite end housed within anend cup y 47. The base of thecup 47 is indented and perforated as shownin Fig. 8 to provide spaced knife edge seats on opposite sides of anopening 43 which receives the pointed end 45 of the blade 36, so thatthe cup 47 and the blade end 45 are confined to a rocking motion withrespect to one another.

The anchored member of the toggle of'the switch consists of thedefiectableactuating .blade 36 the upper end of which communicatesthrough spring .46 with the floating toggle member 38 which is carriedin turn upon the movable contact carrier 30. With the actuating rod 4retracted so as not to apply a pressure upon the blade 36 theelementsofthe switch will assume the position shown in Fig. 4. Theunstresseddivergence of the blade 36 from member 30 acts to maintainblade 36 rearwardly, or to the right as viewed in Fig. 4, so as to bearlightly against the stop 49 that forms a part of the base 16. Thecompression spring 46 urges the spring retainer 38 to pivotcounterclockwise, as viewed in Fig; 4, about the shoulders 34 sothat theshoulders 41 rest against the abutment surfaces 35 of the contactcarrying arms 30. The spring 46 is thus angularly disposed to provide acomponent of force inthe line of action of the contacts 32 to providecontact pressure. The reaction of spring 46 at the same time reenforcesthe normal tendency of the blade 36 tobear against stop 49.

As the actuator 4 is moved forwardly in response to pressure increase inthe bellows housed by the cage 2 an actuating-force is applied tothe-blade 36. The blade 36 is consequently deflected forwardly and actsas a multiplying lever to enlarge small increments of movement of theactuator 4 into corresponding substantial movement at the -end45.Deflection of the blade'and movement of its end 45 carries the spring 46toward alignment with the contact arms 30. The location of the shoulders41 at 'one side of the efiective line of thrust of thespring 46 permitsa substantial obliquity of the spring 46 with respect to the contactarms 30. This obliquity ensures substantial contact pressures untilreversal of the line of :action of the floating toggle 38. Movement=ofthe blade '36 consequently may .be continued to a position nearly inalignment with the contact arms 30' without disappearance of contactpressure. Before such'alignment is achieved the toggle mechanism becomesinvolved in a discharge of'stored energy which ensures a reversal.

Resilience of the blade 36 admits of distortion which results instorageof 'a'slight but'perc eptible amount of springenergy thereinbecause of the thrust of spring 46. As movement of the-blade 36 towarddischarge position is continued'the incidence of the trust of spring 46decreases, thus reducing the component of the force exerted by spring 46acting normal to the path of the end 45 of blade 36. A position isthereforlultimately reached in which the counter-stress in blade 36exceeds the resisting component of spring 46 whereupon, the storedenergy in blade 36 is discharged. At the time of such discharge, theamount of energy stored is sufiicient to invert the floating toggle-38.Substantial contact pressure is thus maintained'up to the time of theinversion.

Snap over is accompanied by a clockwise rotation of spring retainer 38.Shoulders 41 are disengaged from abutments 35 of the contact arms 39 andwithin the space of lost motion of the retainer 38 in which theshoulders- 42.are advancing toward engagement with the arms '30 a rapidbuild up of kinetic energy may occur. The impact of shoulders 42 uponthe contact arms 30 thus delivers a hammerlike blow to aid a rapidexcursion of the contact .32 from the position of rest of Fig. 4 to thepositionof'rest of Fig. 5. The Now delivered not onlyieflects rapidtravel for the contact 32 but may be of suflicient force to break loosesmall welds that otherwise would immobilize the contact 32 and disruptswitch action; 7

Upon retraction of the actuator 4 the action of the toggle will bereversed and the position of Fig. 4 will be resumed. The permanent setof the blade 36 provides for suflicient force to actuate the toggle inthe returning direction.

By placing the end 45 of blade 36 close to the pivots 34 and below thesame the blade 36 may be moved nearly into alignment with the contactarms 30 without causing inversion of the floating toggle 38 and thus theso-called diflerential or space between actuating points may be madequite small. The stable positions of the toggle elements are thusmaintained without snap over or extinction of contact pressure until theblade 36 approaches close alignment with the arms 30. If desired, theupper end of blade 36 may be made to extend slightly above the pivots 34and when such is done a switch reresults which will throw from oneposition of finite contact pressure to another, with no intermediateposition of equilibrium in which contact pressure vanishes, withoutdependence upon storage of energy due to resilience in parts such as theblade 36 or carrier 30. While some advantages may be obtained in thisway, the actuating difierential is increased so that this constructionis less desirable than the one previously described where the end 45 ofthe blade is below the pivots 34 and advantage is taken of stored energyin the blade 36 to maintain contact force until the moment of snap overwhile at the same time reducing the differential movement between snapin opposite directions.

I claim:

1. In a snap action switch a deflectable contact carrier blade anchoredat its inner end and having a deflectable outer end furnishing a movablemounting for an electrical contact, a movable contact mounted on theouter end of said carrier blade, spaced contact arresting means limitingthe excursion of said movable contact, a floating toggle member separatefrom said carrier blade pivotally connected thereto for limited rockingmovement about a pair of spaced aligned pivots on said carrier near theouter end thereof, an inwardly facing spring seat on said floatingtoggle disposed outwardly from said spaced pivot points, a carrierdeflecting expansion spring seated on said spring seat extendinginwardly therefrom towards said spaced pivots and between the sameinclinable with said floating toggle when rocked to impose transversedeflecting forces upon said carrier, an

actuating blade having an anchored inner end and a deflectable outer endextending toward and engaging the inner end of said expansion spring tomaintain a compressive force therein, and means cooperatively engagingsaid actuating blade for moving the defiectable end thereof transverselyof the carrier blade to and from opposite sides of said spaced pivots toreverse the inclination of said expansion spring and floating togglewith a snap action to cause said movable contact to be moved with a snapaction.

2. In a snap action switch in accordance with claim 1 an apparatus inwhich the means for moving the actuating blade consists of transverselymovable means engaging said blade to apply a transverse force thereto at'a point near the inner end thereof.

3. A snap action switch in accordance with claim 1 wherein the spacedcontact arresting means comprise at least one stationary electricalcontact.

4. A snap action switch in accordance with claim 1 wherein said floatingtoggle includes spaced stop means engageable with said carrier blade tolimit the rocking angle of inclination thereof and to engage saidcarrier blade with an impact force when snap action occurs.

5. A snap action switch in accordance with claim 1 wherein the carrierblade comprises spaced side legs joining the inner end thereof with themovable contact mounting and the actuating blade is disposed betweensaid legs and movable across the space between said legs.

6. A snap action switch in accordance with claim 1 wherein spacedstationary stop means are disposed in the path of movement of thedeflectable end of said actuating blade to limit the excursion ofmovement thereof land to contribute to the reaction forces resisting theexpansive force of said expansion spring.

7. A snap switch in accordance with claim 1 wherein the floating togglemember comprises a pair of hooked pivot fingers engaging alignedinwardly extending shoulders on the carrier blade.

References Cited in the file of this patent UNITED STATES PATENTS

